Input : Y ∈ ℂM × L, Φ ∈ ℂM × N, K initialize : Ω ← ϕ, D = [I K , 0 K × (L − K)] ' [u, L, V] = svd(Y) Y red = YVD U = orth(Y red ) \( \Omega =\left\{\mathrm{j}\ \Big|\ c= argma{x}_j\left(\frac{{\left\Vert {\varPhi}_j^H U\right\Vert}_2}{{\left\Vert {\varPhi}_j\right\Vert}_2}\right)\right\},\kern1.25em \mathrm{select}\ K\ \mathrm{column}\ \mathrm{indices}\ (j)\ \mathrm{that}\ \mathrm{maximize}\ c \) \( X={\Phi}_{\Omega}^{\dagger } Y \) output : X, Ω |